Measured under TAPPI T 452, this method lights the sample at 45 degrees and views it straight on, then reports blue reflectance at 457 nm against an absolute scale. Directional geometry responds differently to surface texture and fluorescence than a sphere does, so the reading rarely matches ISO brightness on the same sheet. The GE nickname comes from the General Electric reflectance meter the method was built around.
Customer spec is written in GE brightness, so run T 452 and ISO on the reel sample and report both.
Mill veterans say GE brightness for any 45/0 reading, whoever built the instrument on the bench.
Also heard as
- GE brightness
- directional brightness
- T 452 brightness
Do not mix it up with
- ISO brightness: ISO brightness uses diffuse d/0 geometry, so the two numbers on one sample are rarely identical and cannot be swapped in a spec.
Related terms
Brightness
The blue-light reflectance of pulp or paper, read at an effective wavelength of 457 nm and reported as a percentage.
45/0 geometry
Measurement setup with the sample lit at 45 degrees and viewed straight on, or the reverse.
ISO brightness
Diffuse blue reflectance factor at 457 nm, measured with d/0 geometry and UV content matched to illuminant C.
R457
Notation for diffuse blue reflectance factor at an effective wavelength of 457 nm, the quantity behind brightness.